Acoustic system



Jan. 28., 1969 J. 5. SOUTHARD ET AL 3,424,850

ACOUSTIC SYSTEM Filed Oct. 20, 1965 ACCOMPANIMENT MANUAL 27 TRIGGERREPEATER SPEED 25 CONTROL 4| 35 W34 V D /l INVENTORS 58' 46 4? 36 JAMESS. SOUTHARD CURT R. WOLFANGER BY M4 2 P ATTORNEYS SK Q v- AMPLIFIER -[K]United States Patent Claims ABSTRACT OF THE DISCLOSURE An electronicpercussion device for an electric organ which has a plurality of springsresiliently contacting the diaphragm of the speaker cone. The springsare vibrated by and against the cone when the speaker is driven bygenerated signals to produce a snare drum effect.

This invention pertains generally to an electronic percussion device,and more particularly to an electronic percussion unit for an electricorgan that simulates the sound of a snare drum.

Electric organs have been proposed that include units for making thesounds of various percussion instruments similar to such units containedin pipe organs in theaters and other places. One such unit is describedin a copending application Ser. No. 498,889, filed Oct. 20, 1965, andassigned to the assignee of this application.

It is desirable in such percussion units to include the sound of thesnare drum. This sound, however, is one of the most difficult of all thepercussion instruments to simulate in an electric organ and still use asimple and inexpensive circuit.

It is one object of this invention to provide an electronic percussiondevice that simulates the sound of a snare drum.

It is another object of this invention to provide an electronicpercussion device for use in an electric organ that simulates the soundof a snare drum and is simple and inexpensive to produce.

One feature of this invention is an electronic percussion device havingmechanical vibratory means contacting the flexible diaphragm of aspeaker cone so that the vibratory means is vibrated to produce a snareeffect when the speaker is driven by a generated signal.

Another feature of this invention is a percussion unit for an electricorgan having a speaker with a plurality of springs resiliently connectedto the basket thereof and lying in contact with the flexible diaphragmthereof. The speaker is driven by a generator actuated by the keys onthe accompaniment manual which excite a rate control repeater whichperiodically pulses the signal generator. A decaying signal from thegenerator moves the diaphragm of the speaker to produce an acousticalwave simulating a drum beat, and, the springs vibrate to add the snareeffect.

In the drawing:

FIG. 1 is a rear elevation of the speaker of this invention with thebasket partially removed;

FIG. 2 is a side elevation of the speaker of FIG. 1; and

FIG. 3 is a schematic wiring diagram illustrating one embodiment of thisinvention.

In practicing one specific embodiment of this invention, a speaker, foruse with an electric organ, has a plu rality of springs resilientlyconnected to the speaker basket and which lie in contact with theflexible diaphragm of the speaker cone. Operation of any one of aplurality of keys on the accompaniment manual of the organ energizes atrigger circuit that excites a repeater circuit which has a regulatedrepetition rate. The repeater pulses a signal generator which is coupledto an amplifier circuit.

3,424,850 Patented Jan. 28, 1969 ice The generator produces a decayingsignal which is amplified and coupled to the speaker. The generatedsignal flexes the speaker diaphragm to produce acoustic wavesrepresenting the beat of a drum. As the diaphragm flexes, the springs incontact with it vibrate and strike the diaphragm to produce acousticwaves representing a snare effect. These waves are mixed with the wavesrepresenting the drum beat to simulate the sound of a snare drum.

A better understanding of the percussion unit of this invention may behad by referring to FIGS. 1 through 3 of the drawing. Although the unitis described for use with an electric organ, it should be understoodthat it would find utility whenever it was desirable to have anelectronic percussion unit to produce the sound of a snare drum.

The speaker 10 includes a flexible diaphragm or cone 12 made of asemi-rigid material which is secured to and supported by the speakerframe or basket 14. The diaphragm 12 moves under the influence of avoice coil shown generally at 16 which is secured to the apex of thecone. The voice coil is located within a cylindrical gap of a magnet(not shown) which provides a substantially constant magnetic fieldacross the gap. The magnetic field set up by the audio frequencycurrents within the voice coil interacts with the constant field of themagnet resulting in physical forces being applied to the voice coilwhich tend to move the coil and attached diaphragm in a directionparallel to the axis of the cone. Ideally, an electromagnetic speaker asdescribed will produce an acoustic wave in surrounding means which isthe exact counterpart of the corresponding electrical signal applied tothe voice coil.

Glass filament tape 21 is placed in strips on the exposed walls of thespeaker cone or diaphragm 12. A plurality of springs 20 are resilientlyconnected to the basket 14 by looping each end thereof through the holes22. When attached in this manner the springs lie in contact with theprotective coating of tape 21, on the sides of the cone or diaphragm 12.Therefore, when the audio frequency signal excites the voice coil 16 tomove the core 12 to produce acoustical waves representing the frequencyof the exciting signal, the movement of the diaphragm 12 causes thespring 20 to vibrate and strike the diaphragm. The acoustical wavesproduced by the vibrating springs are mixed with the waves from thediaphragm to produce the desired sound. Tension on the springs 20 can beadjusted so that the springs vibrate at the desired frequency.

How this speaker is adapted as a percussion unit in an electric organ isillustrated in FIG. 3. Actuation of one of the keys of the accompanimentmanual of the organ energizes the trigger circuit 25. The triggercircuit 25 applies an actuating pulse to the repeater circuit 27 as longas a key is operated. The repeater circuit consists of an astablemultivibrator. A variable speed control for controlling the repetitionrate is provided for the repeater circuit 27 and can be adjusted by theorganist to the repetition rate desired. Therefore, when a note isplayed on the accompaniment manual, the voltage pulse will cause therepeater 27 to operate continuously to provide repeating pulses untilthe actuating pulse is terminated.

A switch or stop 30 and resistor 31 couple the pulses from the repeater27 to the signal generator 32. The signal generator produces a burst oftone having a frequency on the order of 166 cycles per second. Adecaying burst is produced each time the pulse is applied thereto.

The signal generator 32 is a phase shift oscillator and includestransistor 34 having a three mesh ladder line connecting the collector35 thereof to the base 36. The line includes resistors 40, 41 and 42 andcapacitors 45, 46 and 47. The pulse from the repeater 27 isdifferentiated by capacitor 50 and resistor 52, with the positive pulsebeing applied through diode 54 across capacitor 46 in the second mesh ofthe phase shift network. The negative differentiated pulse is blocked bythe diode 54. The frequency of the oscillator depends upon the constantsof the ladder line which forms the feedback circuit, and the decaydepends upon the setting of resistor 58 which is bridged acrosscapacitor 46 and controls the Q of the feedback circuit. Thermistor 60provides thermal stability for the oscillator.

The burst of tone from the signal generator 32 is coupled to theamplifier 62 and speaker 10. The acoustic Waves developed by the speaker10 representing the tone burst from the signal generator 32 are mixedwith the acoustic waves caused by the springs being vibrated against thediaphragm by the movement of the diaphragm 12, as heretofore described,to simulate the sound of a snare drum.

What has been described is an electronic percussion unit especiallyadaptable for use in a simple and inexpensive circuit for an electricorgan that includes a unique speaker for simulating the sound of a snaredrum.

We claim:

1. An electronic percussion device including in combination, speakermeans including a movable diaphragm and a rigid support therefor,mechanical vibratory means connected to said support and positioned indirect contact with said diaphragm, signal generator means coupled tosaid speaker means and responsive to the application of a pulse theretofor producing a signal to move said diaphragm to produce an acousticWave representing said signal, said moving diaphragm striking saidvibratory means to generate an acoustic Wave at a frequency other thanthe frequency of said signal.

2. An electronic percussion device including in combination, speakermeans including a movable diaphragm and a rigid support therefor,mechanical vibratory means connected to said support and positioned indirect contact with said diaphragm, signal generator means coupled tosaid speaker means and being responsive to the application of a pulsethereto for producing a signal to move said diaphragm to produce anacoustic wave simulating a drum beat, said moving diaphragm strikingsaid vibratory means to vibrate the same against said diaphragm therebyproducing an acoustic wave simulating the sound of a snare drum.

3. An electronic percussion device, including in combination, speakermeans including a flexible diaphragm and a rigid support therefor,spring means resiliently connected to said support and lying in contactwith said diaphragm, signal generator means, repeater means coupled tosaid generator means and including repetition rate control means, andamplifier means coupling said generator means to said speaker means,said repeater means operating to produce pulses at a rate determined bysaid rate control means, said repeater means being connected to saidsignal generator means so that said pulses from said repeater meansexcite said signal generator means for producing a signal to move saiddiaphragm thereby producing an acoustic wave representing said signal,said diaphragm moving against said spring means and vibrating the sameagainst said diaphragm thereby producing an acoustic wave at a frequencyother than the frequency of said generated signal thereby simultatingthe sound of a snare drum.

4. A percussion device for an electric organ including in combination,speaker means including a flexible diaphragm and a rigid supporttherefor, spring means resiliently connected to said support and lyingin contact with said diaphragm, signal generator means, repeater meansincluding repetition rate control means coupled to said generatorcontrol means, amplifier means coupling said generator means to saidspeaker means, said repeater means operating to produce pulses at a ratedetermined by said rate control means, said repeater means beingconnected to said signal generator means so that said pulses from saidrepeater means excite said signal generator means for producing a signalto move said diaphragm thereby producing an acoustic Wave representingsaid signal, said diaphragm moving against said spring means in contacttherewith to vibrate the same against said diaphragm thereby producingan acoustic Wave at a frequency other than the frequency of said signalto simulate the sound of a snare drum.

5. A percussion device for an electric organ including in combination, aspeaker including a diaphragm and a basket for supporting the same, aplurality of springs resiliently mounted to said basket and each lyingin contact with said diaphragm, a signal generator, an accompanimentmanual and a trigger circuit responsive thereto for providing anactuating pulse, a repeater having a speed control, said repeater beingcoupled to said signal generator and being responsive to said actuatingpulse from said trigger to repeatedly pulse said signal generator at arepetition rate established by said speed control, and an amplifiercoupling said signal generator to said speaker, said signal generatorproducing a decaying signal in response to said pulses to move saiddiaphragm to produce an acoustic wave representing said signal, saidmovement of said diaphragm causing said plurality of springs in contacttherewith to vibrate against said diaphragm thereby generating anacoustic wave at a frequency other than the frequency of said decayingsignal to produce the sound of a snare drum.

References Cited UNITED STATES PATENTS 2,768,235 10/ 1956 Knoblaugh.2,853,145 9/1958 Martin. 3,039,347 6/1962 Krauss et a1. 84l.01 3,149,6929/ 1964 Rehde.

ARTHUR GAUSS, Primary Examiner. B. P. DAVIS, Assistant Examiner.

US. Cl. X.R.

